1. Field of the Invention
This invention relates to improved magnetic record members for use in magnetic recording devices, such as magnetic disks and magnetic drums; and it also relates to a process for manufacturing the same.
2. Description of the Prior Art
In general, a magnetic recording device comprises a recording and/or reproducing head (hereinafter referred to as a "head") and a magnetic record member. One known type of recording and reproducing system used with such a device, is the contact-start-stop (CSS) system.
In the CSS system, a head is first placed in contact with the surface of a magnetic record member. Next, the record member is rotated at a predetermined speed to cause the head to raise up and "float" or "fly" above the record member on a thin layer of air which forms between the head and the record member surface. The desired recording or reproducing (record or playback) operation is then carried out while the head continues to float in this manner. When the recording or reproducing operation is terminated, the record member rotation is stopped and the magnetic head returns into contact with the record member surface.
The frictional force exerted between the head and the record member surface due to such mutual contact during starting and stopping operations causes wear to both the head and the record member, and may eventually damage the head and the magnetic recording medium layer of the record member so that recording and reproducing operations become impossible. Moreover, even a slight variation in the attitude of the head in such a state of frictional contact can impose a nonuniform load on the head that can damage the head and the record member.
Furthermore, large damaging frictional forces can be exerted between the head and the record member even during recording or reproducing operations, in cases where the floating head suddenly and unexpectedly contacts the surface of the record member.
In order to protect the head and the record member from such frictional contact, wear and breakdown, various protective films have been used to coat the surface of the record member.
Some of the heretofore proposed protective films have proven reasonably effective to protect against the types of frictional contact, wear and breakdown discussed above. However, depending on the environmental conditions under which such magnetic recording devices have been used, a large adhesiveness effect has been observed between the head and the record member surface which adversely affects the mechanical stability of the system.
In particular, the following general observations have been made regarding adhesiveness:
(1) Adhesiveness is produced by the presence of a liquid film between the head and the record member, and the amount of adhesiveness increases as the surface roughness of the head and the record member decreases. PA1 (2) The liquid film producing the adhesiveness is formed on the surface of the head and record member when the head slides or runs on the record member surface; and the quantity of such liquid film is particularly large under high humidity conditions. PA1 (3) In the CSS mode, the liquid film formed on the record member surface is scraped by the head so that the film may accumulate in the space between the head and the record member, thereby resulting in adhesiveness.
This adhesiveness effect causes a detrimental increase in the load on the record member drive motor and simultaneously increases the frictional force experienced during sliding of the head on the record member surface, thereby in some cases causing the breakdown of both the head and the record member.
Adhesiveness is a problem, especially with record members used in high-density magnetic data storage and retrieval applications. For such applications, the surface of the record member is highly polished to a smooth specular finish (i.e. a mirror surface) due to the necessity of minimizing the surface roughness of the recording medium layer so as to obtain the desired high-density recording or reproduction characteristics. The surface roughness of the protective film formed on such a specular recording medium layer using conventional methods is generally even smaller than the roughness of the recording medium layer. Hence, since adhesiveness increases as roughness decreases, a large adhesive force is exerted between the head and the record member which affects mechanical stability.